body {
    background-color: gray;
    background-attachment: fixed;
    background-repeat: repeat;
    color: #FFFFFF;
    font-size: 13pt;
}
div {
    width: 700px;
    background-color: #3f3f3f;
    padding: 20px;
    padding-bottom: 40px;
    padding-top: 4px;
    margin: 20px;
    margin-left: auto;
    margin-right: auto;
    border: solid 2px;
}

canvas {
    margin-left: auto;
    margin-right: auto;
    display: block;
}